1. Field of the Invention
This invention relates to an expandable device for insertion into a passage for the purpose of dilating the passage and/or maintaining it open, or occluding the passage and is more particularly concerned with an expandable device for use in medical applications where it can be used to dilate or maintain the luminal patency of arteries and other vessels which may have become partially or completely blocked, or to occlude undesired passages or openings such as between certain arteries or between heart chambers.
2. Description of the Prior Art
The use of expandable devices for insertion into a passage is particularly widespread in the medical field, where such devices are generally referred to as stents. Such stents are generally constructed of metal wire which may be braided (EP-A-0183372), wound (WO/9315661) or knitted (WO94/12136), or alternatively from tubing having perforated walls (WO95/03010).
Current stents are either balloon expanding or self expanding. Balloon expanding stents are the most common and rely on a balloon temporarily placed within the previously compacted stent to distend the stent radially and so lodge the stent firmly against the wall of the vessel within which it is located. However, problems can arise if there is any elastic recoil (i.e. radial contraction) of the stent once the balloon is removed.
Self expanding stents are made from a more elastic material which is constrained to a small diameter for insertion but which will expand to a larger diameter when deconstrained, without the need for any expanding means. Self-expanding stents made of shape-memory material are also known (see for example EP-A-066065). A medical practitioner must be careful in selecting an appropriate stent for each procedure, since situations may arise in which the outward pressure of the stent on the vessel is too great, causing physiological damage, or too small, resulting in dislodgement of the stent.
It is an object of the present invention to provide an expandable device which can be fixed in its expanded condition in a passage, so as to minimise movement of the expanded device in the passage.
According to a first aspect of the present invention, there is provided an expandable device for insertion into a passage, said expandable device comprising a body formed of at least one flexible material, said body being convertible from a collapsed condition in which it is of a size to be inserted into the passage into an expanded condition in which the body is fixed relative to the passage, passage means in said body and extending over at least a region of the body, and inlet means communicating with said passage means to enable a rigidifying material to be introduced into said passage means so that, in use, at least said region of said body can be rigidified whereby to maintain the body in its expanded condition.
Preferably, the body is formed of at least one flexible sheet material. Said at least one flexible sheet material may be elastomeric or non-elastomeric. In cases where the body is formed of two or more flexible sheet materials, each may be elastomeric or non-elastomeric. Said at least one flexible sheet material may be tubular or include a tubular region.
Advantageously, the body in the collapsed condition occupies substantially the same volume as the at least one sheet material. Preferably, the inlet means is closable. Closure may be achieved by, for example, providing the inlet means with a heat-sealable closure, or alternatively the inlet means may be a self-sealing valve.
The device may also include filler means, such as an elongate tube, said filler means communicating with said passage means in the body via the inlet means. The filler means may be used to expand the body of the device and/or introduce the rigidifying material into the body through the inlet means. Preferably, the filler means is separable from the remainder of the device.
According to a second aspect of the present invention, there is provided an expandable device according to said first aspect of the present invention in combination with a rigidifying material for introduction into said passage means through said inlet means.
According to a third aspect of the present invention, there is provided a method of positioning an expandable device according to said first aspect in a passage, comprising the steps of:
(a) introducing into the passage an expandable device according to said first aspect of the present invention with the body being in a collapsed condition;
(b) converting the body into an expanded condition so that it is fixed relative to a sidewall of the passage; and
(c) causing the flowability of rigidifying material introduced into the passage means to be decreased so as to maintain the body in its expanded condition.
Such positioning may be effected to (i) dilate or (ii) occlude the passage, or (iii) maintain the passage at an existing dilation. Additionally, such positioning may be effected to prevent ingress of material into the passage (eg. growths such as tumours in medical applications) and/or egress of material out of the passage, for example, if the passage is damaged (eg. aneurysm).
The body of the device may be inserted so as to be wholly within the passage, in which case fixing of the body relative to the passage is achieved by engagement of a sidewall of the body with the sidewall of the passage.
Alternatively, the body of the device may be inserted so as to be partially located within the passage, in which case said fixing may be achieved by expansion of at least one end of the body located externally of the passage, as an alternative to or in addition to the method of fixing described in the immediately preceding paragraph. Preferably, said fixing is achieved by expansion of opposite ends of the body externally of respective opposite ends of the passage, particularly where said passage is an opening such as between certain arteries or between heart chambers.
The rigidifying material may be a chemically reactive liquid or other fluid which can be caused to solidify, gel or otherwise set or experience an increase in its viscosity when in the passage means in the body. For example, the flowable rigidifying material may be selected from a flowable polymerisable monomer or monomer mixture or a flowable prepolymer, such as an epoxy resin, a silicone elastomer, a cyanoacrylate or methacrylate.
The rigidifying material itself may be used to effect step (b) above by introducing it under pressure into the passage means in the body. However, a hydraulic or pneumatic pressurising medium may be used for this purpose in addition to or instead of the rigidifying material. Additionally or alternatively, a balloon catheter may be used to move the body into its expanded condition.
In one embodiment, the sidewall of the body which engages with the sidewall of the passage in use, is formed of at least one flexible sheet material. The passage means may be disposed inwardly or outwardly of said at least one flexible sheet material or between the flexible sheet materials when more than one is provided. The passage means may be defined at least partly by said at least one sheet material. The passage means may be defined by one or a series of channels extending over at least one surface of said at least one sheet material. When a series of channels is provided, said channels need not be in communication, in which case more than one inlet and filler means may be provided.
Examples of suitable flexible materials for the body include polyesters and polyurethanes. The flexible material may be chemically coated. In particular, the sidewall which engages against the sidewall of the passage may be coated. For example, in medical applications, the sidewall may be coated with cytotoxic agents to treat tumours and/or to discourage tumour growth into the passage. Alternatively, or in addition, a coating of a relatively inert nature may be used to prevent or limit adverse biological reactions between the passage and the body. Examples of such coatings may comprise diamond-like carbon, a ceramic or metals (eg. gold, silver, platinum).
The channel or channels may be defined by two superimposed sheet materials which are sealed together at selected regions so that unsealed regions of the sheet materials define wall of the channel or channels. Alternatively, the channel or channels may be defined on a surface of the sheet material by sealing longitudinal side edges of a suitably shaped strip or strips of flexible material to said surface.
Two or more bodies may be connected in series. Each of the bodies may be provided with its own inlet and filler means so that, in use, each body may be expanded and/or rigidified to a different degree.